The present invention relates generally to magnetic data storage drives. In particular, this invention relates to methods and structures for fly height control.
As the areal density in newer disc drive designs increases, the magnetic spacing and fly height between the pole tips of the read/write heads and the magnetic storage media becomes correspondingly smaller. With these extremely small fly heights, manufacturing variations in the disc topography, particularly during seeking operations, can result in undesired transient mechanical contact between the head and the disc.
To reduce instances of undesired contact, there is a desire to use electrostatic type actuators in fly height control arrangements because of their low cost, low mass and low power consumption. Electrostatic actuators, however, generate an attractive force between the head and the disc that has an approximately inverse square relationship to the spacing. As the head moves closer to the disc, the attractive force increases asymptotically. The electrostatic force can force the head to crash into the disc, resulting in damage to the head, the disc, or both. When the head is very close to the disc and the electrostatic actuator is used, the control of the fly height becomes unstable.
A method and an apparatus are needed to reduce the damage to heads or discs when a disc drive includes an electrostatic actuator controlling fly height spacing and the head contacts the disc.
Disclosed is a disc drive that comprises a disc and a read/write head. The read/write head has an air bearing surface shaped to provide a fly height spacing between the air bearing surface and the disc. The disc has a disc electrical connection and the read/write head has a head electrical connection connected to a conductive region of the read/write head that faces the disc.
The disc drive also comprises a fly height spacing control system including a controller that provides a control signal coupled to the disc electrical connection and the head electrical connection.
The disc drive also comprises a contact sensor. The contact sensor senses an electrical current component of the control signal indicative of contact between the disc and the read/write head. The contact sensor provides a contact sensor output.
The disc drive also comprises a disconnect circuit that couples the control signal to the head electrical connection. The disconnect circuit responds to the contact sensor output and provides a disconnection of the control signal when contact is sensed.
These and various other features as well as advantages that characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.